I received an email today and I would like to know if it's true. It says there are people hanging around dance clubs with stickers that say "Welcome to our world." The stickers are filled with tiny needles carrying AIDS-infected blood, and once a sticker is stuck on you, you contract the AIDS virus. They just choose victims at random. I don't believe that it is possible to contract the disease that way. Is this a hoax?

C.M.

Your question is extremely common. Even before the Internet became popular, there were rumors like this. Now they have become more pervasive. The most common rumor is of tainted needles being left on movie-theater seats.

First, let me say that I have never heard of any incident similar to this reported in the press or in the medical literature. That is not to say that it could never happen. Someone could always decide to commit a copycat crime based on the very same email that you read. But I think it would be very unlikely, and I personally do not worry about it at all. For one thing, it seems like a lot of trouble for a person to go through just to infect someone. In addition, the person has the threat of being caught and sent to prison. While there are people who will kill for no reason, I think that the risk of this form of attempted murder would be much, much lower than the usual threat of guns and other weapons, a risk that most of us ignore every day.

Even if the email you read were true, it is by no means certain that this method would actually cause anyone to develop AIDS. One can certainly become infected if a needle tainted with the virus breaks the skin, allowing the microbe to enter the immune cells where the virus replicates. There are numerous reports of health-care workers becoming infected with HIV after accidental needle sticks. The risk of acquiring HIV after such an exposure is about 1 in 300. While this seems high because HIV is fatal, it is far from a certainty. Generally, a large needle causing a deep injury poses the highest risk.

Another level of reassurance comes from the fact that treatment is available to minimize the risk of HIV after needle sticks. The procedure for health-care workers is to first have the needle tested to see if it is indeed tainted with HIV. Most workers begin taking medication to stop HIV while waiting for the results on the needle to come back. Then, if the needle is not tainted, the medication can be stopped. While the studies on such preventive treatment are few, most infectious-disease experts believe it is beneficial.

So the next time you get a scare email like that one, realize that it is probably a hoax. Do everyone a favor by deleting such messages rather than forwarding them to friends who may not be so skeptical or so well informed.